In the mold clamping device, a movable platen and a movable mold move reciprocally. Safety of workers and operators is ensured by surrounding the mold clamping device with a safety cover.
One example of such safety covers for the mold clamping device is disclosed in Japanese Patent No. 3265104, and is known in the art.
The safety cover disclosed in Japanese Patent No. 3265104 will be described with reference to FIG. 7 to FIG. 9 of the accompanying drawings.
As shown in FIG. 7, a lateral frame 101 extends horizontally, and a lower frame 111 is arranged below the lateral frame 101. A safety door 105 is attached to (across) the lateral frame 101 and the lower frame 111. The safety door 105 moves horizontally. In FIG. 7, the safety door 105 is in an open position. An operator can physically enter the inside from an opening 107.
When the operator enters the inside from the opening 107, the lateral frame 101 becomes an obstacle. This will decrease the work efficiency of the operator.
There is a demand for a structure that can improve the work efficiency. A structure that meets such demand will be described with reference to FIG. 8 to FIG. 9.
As shown in FIG. 8, a lateral frame 101 extends in a direction perpendicular to the drawing sheet. A lower frame 111, which has a rectangular cylinder shape, is arranged below the lateral frame 101. The lower frame 111 also extends in a direction perpendicular to the drawing sheet.
A casing 102 is secured to the lateral frame 101. A cross-sectional shape of the casing 102 is “C.” A first movable member 103 is received in the casing 102. A cross-sectional shape of the first movable member 103 is “C.” A second movable member 104 is received in the first movable member 103. A cross-sectional shape of the second movable member 104 is “H.” The first movable member 103 moves relative to the casing 102 in a direction perpendicular to the drawing sheet. The second movable member 103 moves relative to the second movable member 103 in a direction perpendicular to the drawing sheet.
An upper portion of a safety door 105 is attached to the second movable member 104 with bolts 106, and a lower portion of the safety door 105 is placed on the lower frame 111 via wheels 112.
The safety door 105 moves along the lateral frame 101 and the lower frame 111, and is brought into an open state or a closed state.
FIG. 9 is a perspective view useful to describe a front end (free end) of the lateral frame.
As shown in FIG. 9, the C-shaped casing 102 is secured on a front end of the lateral frame 101. The C-shaped first movable member 103 is received in the casing 102 such that the first movable member 103 can move in an axial direction. The H-shaped second movable member 104 is received in the first movable member 103 such that the second movable member 104 can move in the axial direction. The safety door 105 is secured to the front end of the second movable member 104 with the bolts 106.
Having a so-called telescopic structure, the first movable member 103 has a smaller diameter than the casing 102, and the second movable member 104 has a smaller diameter than the first movable member 103.
A force F1 may act onto the front end 105a of the safety door 105 from the outside toward the inside. The second movable member 104 has a cantilevered structure, and a maximum displacement occurs at the front end. In addition, the second movable member 104 has smaller bending rigidity (flexural rigidity) than the first movable member 103 and the casing 102.
Consequently, the force F1 displaces the front end 105a of the safety door 105 even if the force F1 is small.
From the viewpoint of safety, the safety door 105 needs to have rigidity. If the second movable member 104 has a large diameter, it is possible to decrease or suppress the displacement. However, if the second movable member 104 has a large diameter, the first movable member 103 has a large diameter, and the casing has an even larger diameter. Thus, the weight increase of the first and second movable members and the casing is not avoidable, and the material cost increase of the first and second movable members and the casing is not avoidable.
When the safety door 105, which is indicated by a phantom line in FIG. 9, is looked at, the safety door is connected to the second movable member 104 with the bolts 106. Thus, a certain load acts on the connecting part between the safety door and the second movable member. Accordingly, it is necessary to reinforce the safety door 105 in the vicinity of the connecting part, i.e., at an upper side of the safety door 105.
In view of the foregoing, there is a demand for a safety cover that can avoid a significant cost increase in reinforcing the upper side of the safety door 105, and allows the second movable member 104 to have a large diameter without influencing the casing 102 and the first movable member 103.